Apologies up front, this is not a DIY question but a work related one
Do all S Plans needs an automatic bypass? I assume that they do.
I am getting grief off a customer who has an S plan with no bypass, the valves close and the pump over run is then causing the boiler over heat switch to kick in. The plumber, who is a friend of the customer, keeps telling them that the wiring is wrong. I think the plumber is a bell end.
A quick check on the Honeywell site says that bypasses are needed. Is there chapter and verse anywhere else to say that they are needed?
Adam